1. Field of the Invention
The present invention relates to a method and an apparatus for the ozone treatment of effluent, using ozone mixed with hydrogen peroxide, in which effluent is treated by ozone mixed with a little hydrogen peroxide, particularly, to such a method and an apparatus, which improve the ozone performance without reducing the efficiency of the removal of the total organic carbon (hereinafter called TOC) from effluent.
The term "ozone performance" means amount of ozone for treating unit amount of TOC, and is expressed as .DELTA.O.sub.3 /.DELTA.TOC in this specification and claims.
2. Description of the Prior Art
Japanese Patent Application JP-A-5-228481 discloses an ozone treatment using ozone mixed with hydrogen peroxide, in which hydroxyl radicals (OH radical) are effectively generated as a product of a reaction between the ozone and the mixed hydrogen peroxide. The hydroxyl radical possesses far stronger oxidizing and decomposing power than that of hydrogen peroxide or ozone, and can decompose and remove persistent substances in effluent.
The OH radicals and the HO.sub.2 radicals indirectly react in the presence of intermediary ozone molecules in the effluent, and they form a complex chain reaction system.
It is considered that following processes occur simultaneously in the effluent under the ozone treatment using ozone mixed with hydrogen peroxide:
An initiation process to generate radicals as a product of the ozone and the hydrogen peroxide;
A propagation process to advance the chain reaction, consuming the radicals in the presence of intermediary ozone;
And a termination process, in which the OH radicals react with the organic compounds in the effluent.
The reaction in the ozone treatment using ozone mixed with hydrogen peroxide is very complex, because many reactions simultaneously take place and the reactions interfere to each other. Thus the control of the reaction, which involves radical reactions, was very difficult. For example, by simply increasing the concentration of the ozone, the TOC in effluent can be decreased, on other hand, the ozone performance in the treatment declines, namely the amount of ozone O.sub.3 for treating unit amount of TOC increases.
Moreover, the operation conditions for the ozone treatment, for example, the quantity of the hydrogen peroxide, the concentration of ozone, etc, are not optimized. Additionally, the optimal conditions for the ozone treatment, in case that ozone gas is injected into effluent at many injection points, are entirely unknown.
Thus, the ozone treatment using ozone mixed with hydrogen peroxide is so estimated that it is not advantageous from an economical point of view and it is difficult to control from a technical point of view.